Variable-capacity metering pump



Nov. 27, 1956 D. B. HoRToN ETAL 2,771,846

I VARIABLE-CAPACITY METERING PUMP Filed May 17, 1954 4 Sheets-Sheet 1Nov. 27, 1956 D. B. HoRToN ET Al. 2,771,846

VARIABLE-CAPACITY METERING PUMP 4 Sheets-Sheet 2 Filed May 17, 1954 Nov.27, 1956 D. B. HORTON ET AL 2,771,846

VARIABLE-CAPACITY METERING PUMP Filed May 17, 1954 4 Sheets-Sheet 3 BYMaw )l ATTORNEYS Nov. 27, 1956 D. B. HORTON ET AL 2,771,846

VARIABLE-CAPACITY METERING PUMP Filed May 17,' 1954 4 Sheets-Sheet 4mwnmm mfg A Mgg V524 //6 f l'ff// INVENTORS VARIABLE-CAPACITY METERINGPUMP Donelsou B. Horton and Douglas Johnston, Huntsville, Ala.,assignors to John Blue Company, Incorporated, Huntsville, Ala., acorporation of Alabama Application May 17, 1954, Serial No. 430,087

4 Claims. (Cl. 10S-203) This invention relates to variable-capacitymetering pumps, and more particularly to pumps for metering apressurized normally-gaseous liquid. This invention is an improvement onthe metering pump disclosed and claimed in the copending application ofJohn Blue, Serial No. 80,957, tiled March ll, 1949, now Patent No.2,696,785.

The pump disclosed in the aforementioned application is used principallyto accurately meter anhydrous ammonia for application to the soil foragricultural purposes. While very satisfactory for its intended purposein actual practice, the pump is subject to several improvements whichboth increase its metering accuracy and reduce maintenance expense. Thepump disclosed in Vthe above application is of the positive displacementtype, having a piston or pump plunger provided with an in-let checkvalve and reciprocable in a pumping cylinder. The cylinder is providedwith an outlet check valve that is loaded by the pressure of the sourceof supply of the liquid being pumped independently of the discharge fromthe pump. The piston rod or pump rod is intermittently engaged andpushed inwardly of the pumping chamber for a discharge or pumping strokeby either a reciprocating crosshead driven by a connecting rod andcrankshaft arrangement or a rotating cam. The suction stroke of thepiston rod, -i. e., movement of the rod outwardly of the pumpingchamber, is effected by springs and also by the pressure of the sourceof supply of the liquid being pumped. The pump is of variable capacity,and the capacity is adjustable by means which serve to limit the strokeof the piston rod.

In the aforedescribed pump, when its capacity is adjusted to a settingbelow maximum, there is lost-motion engagement between the reciprocatingcrosshead or rotating cam and the piston rod. It also will be seen that,as the setting of the pump is progressively adjusted toward minimum, theextent of lost motion in the aforementioned engagement increasescorrespondingly. Further, it will be seen that, since the suction strokeof a pump is effected solely by the aforementioned springs and thepressure of the source of supply of the Huid being pumped, the suctionstroke is not accomplished by a positive drive. ln the event that thepacking gland for the piston or pump rod is too tight, the piston rodmay tend to stick so that a full suction stroke, at the adjusted settingof the pump, i-s not obtained, with consequent metering inaccuracies.The same result can possibly obtain at higher rates of pump operation,in that a full suction stroke may not occur before the piston rod isagain engaged by the positive drive for its discharge stroke.Furthermore, because the suction stroke of the pump is not obtained by apositive drive, the drive for the pump is under an intermittent orpulsating load.

Additionally, the pump shown in the aforementioned application has avalve-controlled purging passageway extending between the pumpingchamber and the outlet chamber at the discharge side of the outlet checkvalve.

2,771,846 Patented Nov. 27, 1956 The valve controlling the passagewaymust, of course,

within the pumping chamber.

In addition to the foregoing, the pump shown in the aforedescribedapplication has a partially-open crankcase so that a portion of thepiston or pump rod, and the mechanism for adjusting its stroke, areexposed. Since the pump is utilized by farmers, there is a stronglikelihood of dirt or trash accumulating in the aforedescribed expo-sedportion in the crankcase with resultant undue wear and abrasion of thethus-exposed moving parts of the pump.

Therefore, it is an object of this invention to provide avariable-capacity metering pump of the reciprocating type whereinpulsa-tions in the load on the pump drive are smoothed out as much aspossible and the evenness of the load on the pump drive is at maximum.

It is another object of this invention to provide a pump of the typedescribed that -is accurate at higher rates of operation.

It is another object of this invention to provide means for purging thepumping chamber of the type described which eliminates the need for ahigh-pressure valve.

it yis another object of this invention to provide a pump tof the typedescribed that has a housing completely enclosing all moving parts ofthe mechanism for adjusting the capacity of the pump. l

Other objects and advantages of the invention will become apparent fromthe following description and accompanying drawings, in which:

Figure 1 is a side elevational view of a metering pump embodying thisinvention.

Figure 2 is a plan view of the pump shown in Figure l, with parts brokenaway.

Figure 3 is a longitudinalsectional view taken on lines 3 3 of Figure 2and showing the pump adjusted to its maximum capacity.

Figure 4 is a view corresponding to Figure 3, but showing the pumpadjusted to a less than maximum capacity.

Figure 5 is an enlarged fragmentary top plan view of the pump shown inFigure 2, with parts broken away to lillustrate details.

Figure 6 is an enlarged vertical sectional view taken on line 6-6 ofFigure 1.

Figure 7 is an enlarged vertical sectional View taken on line 7 7 ofFigure 3.

Figure 8 is an enlarged fragmentary sectional view taken on line 8-8 ofFigure 2.

Figure 9 is an enlarged fragmentary sectional view taken on line 9--9 ofFigure l.

Referring now to the drawings, there is shown a pump embodying thisinvention. The pump includes an openended cylinder 10 having exteriorcircumferential end flanges 12 and 14 and a liner 16 iitting against aninterior shoulder 18. Engaging against the other end of the liner 16,with a gasket 20 therebetween, is a plug-like member 22 having a centralvalve port 24 therethrough provided with an annular valve seat 26 at itsouter end. A flanged cylinder head 28, secured by ycap screws 30 to thecylinder tiange 14, has an annular boss 32 fitting into one end of thecylinder 10 and engaging against the plug-like member 22, with anappropriate gasket 34 therebetween to retain the member 22 and the liner16 in proper position within the cylinder. The boss 32 is provided witha central circular recess 36 opposed to the valve seat 26 to form adischarge chamber 33 from which a passageway 40 leads to aninteriorly-threaded opening 42 (Figure 8) in the cylinder head 30 forconnection to a discharge conduit or hose 44. A valve disc 46 having arecessed resilient valve washer 48 secured thereto by a screw 50 isadapted for seating engagement with the valve seat 26.

3 The valve disc 46 has a stern 5K2 slidably guided in a bore 54 in thecylinder head 28 for reciprocating seating and unseating movement of thevalve disc. At its rearward end, the valve stem 52 has a reduced andthreaded extension 56, with a flexible sealing cup 58 and a rigidcupretainer Washer 6i) secured thereon by an elongated nut 62 having alocking set screw 64 threaded into the other end thereof. A coilcompression spring 66 is engaged between the nut 62 and a plug 68threaded into the outer end of the bore 54 for urging the valve washer48 to seat.

The ange 12 at the other end of the cylinder 10 is secured to an openend of a crankcase housing 70, as by cap screws 72, with a stuting boxplate 74 clamped therebetween. The stufling box plate 74 has a circularportion 76 extending into the corresponding end of the cylinder toclosethe same and a circular portion 78 on its opposite face extendinginto a circular opening 8l) in the crankcase housing 70 to close thesame. An appropriate sealingV gasket 82 is interposed between thecylinder 10 and the sniffing box plate 74. Reciprocable within thecylinder liner 16 is a valved pump plunger or piston 84 having a pistonrod or pump rod 86 threadedly engaged with one end thereof and slidablyextending through a stuing box88 in therstuffing box plate 74 and intothe c rankcase housing 70. The piston 84 is provided with a cup seal 90secured in place by a cup-retainer washer 92 and snap ring 94 (Figure3), and has a plurality of ports 96 extendingtherethrough from end toend thereof. The piston 84 divides the cylinder 10 into a pumpingchamber 98 and an inlet chamber 100 to which a suction line 102isconnected. The ends of the piston ports 96 which are exposed to thepumping chamber 98 are arranged in a circle and normally closed by avalve disc 104 reciprocable on a valve stud 106 centrally threaded intothe corresponding end of the piston 84. The valve disc 104 is urged toseat against the end of the piston 84 to close the valve ports 96 by acoil compression spring 108 surrounding the stud 106 and retainedthereon by a retainer washer 110held on the stud by a snap ring 112.

In operation, the pump is mounted on a tractor on a towed type ofvehicle (not shown) and driven by mechanism later described by a drivefrom a ground-engaging Wheel of the vehicle. The liquid to be pumped, e.g., anhydrous ammonia, is contained in a supply tank (not shown), alsomounted on the vehicle. Liquid anhydrous ammonia, when coniined,develops considerable pressure at ordinary room temperature, and whenexposed to the heat of the sun in the aforementioned supply tank,develops an even greater pressure. Hence, this pressure of the liquidbeing pumped would require an extremely heavy and strong spring 66 forthe outlet check valve 46 of the pump, were such spring the onlyinstrumentality used to urge the outlet check valve to seat. To avoidthis diiiculty, the outlet check valve 46 of the pump is loaded by thepressure of the source of supply of the uid being pumped. To this end, ahousing 114 is secured, as by cap'screws 116, to thetop of the cylinderhead 28 and has a bore 118 (Figures 8 and 9) aligned with a radial port119 inthe cylinder head that is in communication with the bore`54 in thecylinder head rearwardly of the cup seal 58 on the valve stern 52. A'conduit 120 connected to the inlet chamber 100 of the pump and to thebore 118 in the housing 114 conducts the pressure of the iiuid beingpumpedto the bore 54 at the rear of the valve stem 52, to thusconstantly urge the valve 46 to seat. lPreferably, the diameter of thevalve stem 52 and they valve port 24 are equal, so thatpthe valve 46 issubstantialiy pressurebalanced. Also, the bore 118 preferably includes achoke oritice 122 therein, for reasons described in theabovementionedcopending application.

The pmpthus'farshown and described is substantiallyV Before thelstangata pumping operation, becausethe Pump is. normally exposed t0 theheat Qt the, Sun, assistedescribed, the pumping chamber 98, inletchamber 100, and the suction line 102 leading thereto are apart to befull of gas, or a mixture of gas and liquid. Since a mixture of gas andliquid cannot be metered with any degree of accuracy by the pump, itusually is essential to purge the pumping chamber 98, inlet chamber 100,and the supply line 102 leading thereto of gas before the starting of apumping operation and to till such chambers and line with liquid. Forthis purpose, a two-part operating shaft 124 (Figure 9) extends througha stufling box 126 in the housing 114 transversely through the bore 118and has a handle 128 on one end thereof for rocking the same.y The twoparts 130 and 132 of the shaft 124 have threaded connection within thebore 118, and the corresponding end of the part 138 of the shaft issquare, as at 134, for the rigid mounting of a lever 136 thereon thatdepends through the bore 118 and port 119 into an annular groove 138 inthe nut 62. Accordingly, rocking movementl of the shaft 124 engages thelower end of the lever 136. with a side wall of the groove 13.8 tounseat the valve 4 6'. Upon release of the handle 128, the spring 66immediately reseats the valve 46 with a normal seating force. The part132 of the shaft extends into an exterior counterboret' 140 in thehousing 114 and is retained therein by a snap ring 142 engaging theouter end of a sleeve 144 surrounding the shaft part 132, the inner endof the sleeve engage ing against the bottom of the -counterborePreferably; a cap-like plug 146 is threaded into the counterbore 140l toprevent leakage.

For driving the pump, a crosshead 148 (Figures 3 and 4) is reciprocablymounted in .a longitudinal guiding bearing 149 formed interiorly `of thecrankcase housing 70. The crosshead 148 is driven by a crankshaft 150;transversely journalled in the housing 70, and connected to thecrosshead by a connecting rod 152. One end (of the crankshaft 150projects out of the housing 70 for drive by a Vchain 154, engaging asprocket on a ground-engage.. ing wheel (not shown) of the vehicle onwhich thepurnpr is mounted and a sprocket (not shown) rotatably mountedon the outer end of the crankshaft. Appropri` ate clutch mechanism (notshown), such as tha-t shown -in the aforementioned application, isemployed to en-f gage and disengage the crankshaft sprocket into andtromdriving connection with the crankshaft 150.`

The crosshea-d 148 has a cylindrical recess `156 a-t the forward endthereof to define an integral forwardly-.pro-y jecting sleeve 158coaxial with and receiving the rearward; end of the piston rod 86. Thebottom 160 of.this.re cess 156 is dat for engagement with thecorrespondingly-.` at end of the .piston rod 86 to intermittently pushthe .latter inwardly of the pumping chamber 98 for a pumping ordischarge stroke of the piston 84. Threaded into the end of the sleeve158 is a collar 162, the inner endof which `forms an .abutment forengagement with a 'cor-g responding abutment formed by acircumferentialzange .164 on a nut 166 engaging a threaded portion 168of the .piston rod 86. A lock nut is also threaded'onto the piston rod86 for engagement with the forward veudof the Anut 166. A side of thethreaded portion 168 of lthe piston rod 86 is flattened and has anelongatedA scale 172 secured thereto for cooperation with the forwardendof the lock nut 170 to indicate the relative positionof the adjustingnut 166 with respect to the piston rod 86. This scale 172, as willbecome appa-rent, can'ibe graduated to 4indicate -the capacity of thepump, i. e.; vvthe adjusted capacity of the pump between maximum" and.minimum or zero capacity.

In the showing of Figure 3, the pump is adjusted to capacity; i. e.,atthe beginning of a dischargeA stroke of the crosshead 148, the bottom160 of the -recessxl engages the end ofthe piston rod -86 so thatiapumping `strokewof maximum Vlength will beeffectedf. Likewiseit will fbeseen that the ange y164 on the nut166.amzlgtlre collar 416,2, areengaged fso that .on thereturn-strokenfg.

arrastre the crosshead 148 the length of the suction stroke of thepiston 84 will be at -a maximum.

Referring now to Figure 4, vit will Ibe seen that in this showing theadjusting nut 166 has been threaded rearwardly on the piston rod 86, sothat in its return stroke the 4cross-head 148 will not pull the pistonrod 86 rearwardly .as far as when the nut 166 is in the position shownin Figure 3. Accordingly, as the `crosshead 148 s-tarts its dischargestroke, it moves a considerable distance before eng-aging the end of thepiston rod 86 to effect the discharge stroke of the same. Consequently,a lost-motion connection exists between the piston rod 86 and thecrosshead 148 at .any position of adjustment of the nut 166 betweenminimum .and maximum capacity of the pump.

As described before, the inlet chamber 100 and the pumping chamber 98 of.the pump .are under considerable pressure even during the suctionstroke of the piston 84. This pressure, of course, urges the piston rod86 outwardly of the pumpin-g chamber 98. Thus, while once the crosshead148 engages the piston rod 86 the crosshead and the crankshaft 1'50 andits drive are under considerable load during the pumping stroke of thecrosshead, unless otherwise provided for the crosshead and its drive areunder no load on the suction stroke. Therefore, unless otherwiseprovided for, the drive :for the pump would be under a pulsating load,which wou-ld result in considerable wear and tear and possible breakageof some of the parts of the pump drive.

In order to eliminate this difiiculty, a two-part transverse crossbeam174 has its upper land lower parts clamped onto a reduced portion of thepiston rod 86 and engaging against a rearwardly-facing shoulder 176thereon. Clamped between the two parts of the crossbeam 174, at each endthereof, is a necked portion of a rod 178 which extends parallel to theaxis of the piston rod l86 through yaligned apertures in the crankcasehousing 70 and in the stuffing box plate 74 and outwardly along theIcylinder 10. On the outer end of the rod 178 is a spring-retainerwasher 180, retained by a snap ring 182, and -between the washer 180 andthe bot-tom 184 of a counterbore extend-ing through the stuing box plate74 and into the housing 70 is la coil compression spring 1-86.Preferably, each spring 186 is enclosed in a separate tube 188 havingone end thereof threaded into the -ange 12 (Figure 5) on the end of thecylinder 10 and the other end thereof Iclosed by a threaded plug 190.The intermediate portion of each tube 188 is supported -in an aperturedear 192 on Ithe flange 14 on the other end of the cylinder 10.

From the aforedescribed construction, Iit will =be seen that -thesprings 186 oppose the suction stroke of the piston rod 86 so that thedrive for the pump will be under a load during `the suction stroke ofthe latter. At the same time, the springs 186 s-tore up energy tosomewhat relieve the load .on the pump drive during the discharge orpumping stroke of the pump. Thus, when the pump is adjusted for lessthan maximum capacity and the crosshead 148 starts its discharge stroke,the springs 186 tend to maintain the ange 164 on the adjusting nut 166in engagement with the end of the collar 162 for an appreciable extentof the discharge stroke of the crosshead 148 and until the pressure inthe pump chamber 98 is built up to such an extent that the springs 1'86cannot overcome the same. At this time, the bottom 160 of the recess 156Iin the crosshead 148 catches up with and engages the end of the pistonrod 86 to eiect a positive pumping stroke of the latter. Therefore, itwill lbe seen that jars and impacts occasioned lby the lost-motionconnection between the piston rod 86 and the ycrosshead 148 aresubstantially lessened and minimized by the action of the springs 186.

Referring now to Figures l to 6 of the drawings, it will be seen thatthe crankshaft housing 70 includes two chambers 194 and 196 joined by alower passageway 198 beneath the crosshead bearing 149, the chamber 194serving as an actual crankcase and the chamber 196 serving as a housingfor the pump-capacity-adjusting mechanism and for the exposed portion ofthe piston rod 86 and exposed ends of the spring rods 178. In operation,the crankcase chamber 194 normally has oil therein which can flow, viathe passageway 198, into the chamber 196 to maintain the moving partstherein in a lubricated condition. The top of the chamber 196 is open,save for a longitudinally-extending bridge member 200, and the upperedges of the end walls of the chamber 196 are inclined laterally anddownwardly to provide two upper openings 202 and 204 (Figure 6) to thechamber, one on each side of the bridge member 200, the upper edge ofeach opening lying in a downwardly and laterallyinclined plane. Closingthe opening 202 is a closure plate 206, secured to the housing 70, as byscrews 208. An apertured ear 210 at the lower edge of the closure plate206 has a wing bolt 212 extending therethrough and into a tapped openingin the crankcase housing 70. The opening 204 on the other side of thebridge member 200 is closed by a similar closure plate 212 having atransparent window 214 therein for viewing the scale 172. The closureplate 212 is similarly secured in position by a wing bolt 216, but hasno other securing screws. At their upper and adjacent edges, bothclosure plates 206 and 212 are provided with transversely-overlappingapertured ears 218 and are pivotally connected together by alongitudinally-extending pivot pin 220, so that either closure plate maybe unfastened from the crankcase housing 70 and raised upwardly forinspection of the interior of the chamber 196 and the parts therein.

Considering again the mechanism for` adjusting the capacity of the pump,it will be seen that at each discharge stroke the piston 84 is pushedinwardly of the pumping chamber 98 almost into engagement with themember 22, so that at each discharge stroke of the pump the volume ofthe pumping chamber 98 is reduced to a minimum. Because of this fact,even if some gas is formed or enters into the cylinder, the effect ofsuch gas on the accuracy of metering of the pump is minimized. On theother hand, if the volume of the pumping chamber is not reduced to aminimum at each discharge stroke of the pump and gas is formed or entersinto the pumping chamber, such gas might tend to accumulate until thepump became gas-locked.

It thus will be seen that the objects of the invention have been fullyand effectively accomplished. It Will be realized, however, that variouschanges may be made in the specific embodiment shown and described forthe purpose of illustrating the principles of the invention. Therefore,this invention includes all modifications encompassed within the spiritand scope of the following claims.

We claim:

1. A pump for accurately metering a pressurized normally-gaseous liquidcomprising: means defining an eX- pansible pumping chamber having aninlet and an outlet; an inlet check valve and an outlet check valvecontrolling said inlet and said outlet, respectively; means operable byliuid pressure for loading said outlet check valve independently of thedischarge from said outlet; conduit means for supplying said fluidpressure operable means with pressure liuid from the source of thepressurized liquid being pumped; and manually-operable means having alost-motion connection with said outlet check valve for opening thelatter to purge said pumping chamber, said manually-operable means beingnormally at rest during movements of said outlet check valve occasionedby metering operation of said pump.

2. A pump for accurately metering a pressurized normally-gaseous liquidcomprising: means defining anV eX- pansible pumping chamber having an.inlet and an outlet; an inlet valve and an outlet valve controllingsaid inlet and said outlet, respectively, said inlet valve being:aacheck valve andsaid outlet valve having areciprocab'le valveinengberc'vvhichi's urged .to' open Yby pressure'lin said chambermeans'operable .by luid pressureinrdependent tensionextends into a spaceseparate from `and out of .communication withthe discharge from 4theoutlet, and tlieman'ually operable means includes a lever .having lost-.motion .engagement .with said extension, `whereby said lever isunaffected by reciprocating movements of the .valve .member effected byoperation of the plunp.

A vpumpifor accurately metering a` pressurized nor- .mally-gaseousliquidcomprising: lmeans defining an ex- .pansible pumping chamber having aninlet and an outlet;

,an .inlet valve and an outlet valve controlling said .inlet kand saidoutlet, respectively, said inlet valve` being a `'check 'valve and saidoutlet valve having a reciprocable Avalve member which is urged to'openby pressure .in

said chamber; means operable by fluid pressure independent of thedischarge from said outlet for urging said .outlet valve `to close, saidfluid pressure operable means including ahousing; conduit means operablyassociated `with said housing for supplying said pressure operable meanswith pressure uid from the source of the pressurized liquid beingpumped; an extension on `said outlet .yalve' ,member opposite saidoutlet,-outside said cham- Pump- '.lber, land withinrsaid housing;andilever. means .mounted for pivotal movement.:'onlsaidmousing,.,xtrdnggtosthe eirterioi' thereof .iff manual operation, `and rhaving.lost- -motinienga`gement withfsaid extensionforopening sid.outlet..valve memberlto purge said lpumping chamber,

said lostmotionenga'gementserving 'toallow said lever .means .toremainlat rest Vduring metering operation lof said.1References',Citedinrthe Viile ofv this patent umm STATES .PATENTS

